Installing A Skylight Home Improvement
Putting in a skylight is a big job, but it comes with a big reward – it’s hard not to appreciate the effect it can have by bringing natural daylight to an area that has no windows.
There are other write ups about skylight installations around the web, and a really good one is this one, by Matthias Wandel. In it, he covers all of the details – from beginning to end. In this article, I want to concentrate on the interior work to finish the installation, leaving out the part where the actual skylight was cut into the roof, since the details for this are fairly typical.
First, some history. When I bought the house, it had two ‘light tubes’ – tubular skylights installed, one in the upstairs hall and the other in the main upstairs bathroom. These look like this:
Unfortunately, these did very little to brighten the two areas and were plagued with other issues. They leaked, were not properly insulated against the winter cold and were poorly sealed. This was not a defect with the manufacture, but with the installation. I’m sure these units can be very effective under the right circumstances, providing they are correctly installed.
I decided to replace these with real skylights at the first opportunity and when I found two on sale, I bought them. I then installed the skylights in the roof, knowing that I would get around to the interior work later. It’s good to know that a project like this can be done in two stages.
In order to more efficiently do the work in the ceiling, I needed to take the stair railing out and build a work platform:
This was really the best way to go, since the skylight is directly above the stairs. Removing the railing was something I had to do anyway, as I would be rebuilding these stairs and railing eventually. The platform is just a piece of 1/2″ plywood supported on the upper landing on one side and a wood frame on the other. With everything screwed in place, this makes it a lot safer and more convenient to work above the stairs.
With the platform done, I took out the lens of the light tube. This was the only part of the unit left, since I’d taken out the tube itself the previous summer when I installed the skylight.
Using the tube light hole to get bearings on the skylight in the roof, I made layout lines on the ceiling and cut out the drywall. I used a drywall saw, being careful not to cut any of the electrical wires. With the ceiling opened, the skylight is visible and I can see the framing that needs to be altered. The wiring for the light fixture has to be moved as well.
The original framing is 16″ on centre and that made it impossible to place the skylight between rafters. I have a roof rafter to cut that’s in the middle of the skylight and also a ceiling joist to cut.
This is where it has to be determined what effect cutting these framing members will have. In this case, the load that the rafter carries could be transferred to the adjacent rafters with headers, since the skylight was narrow and the span short. The only load the ceiling joist had was the drywall ceiling itself, so adding headers to the opening supported it. It’s important to note that when structural framing members are cut, the loads they carry need to be adequately supported.
Unrelated to the skylight installation, a year earlier I had done some structural work throughout the house and some of this was in the attic. I changed a few rafters into trusses that I built in place. A portion of a truss is visible in this picture. The roof was traditionally framed but not very well done and had started to sag slightly. The trusses were made to help shore up the roof and take some of the load off the central partitions.
With the rafter and joist cut out, headers are installed and the well is ready for framing. Also seen in the picture above is the new location for the light fixture (right side of the photo). Luckily, there was enough wire in the original runs to move the light without much trouble:
Finished for the day, I used plastic to cover the hole overnight.
Insulating a skylight well is important – a lot of heat can be lost if it is not done properly. It is difficult to do with fiberglass batts, since the framing used is not usually deep enough to hold it in place. In this instance, I had very little space on either side and had to use 2″ x 2″ to frame the well. For this reason, I chose to use rigid insulation boards which I fastened to the back side of the framing:
The framing is screwed together and in place. This framing transfers some of the roof load to the ceiling, therefore it needs to fit well and securely fastened to avoid movement that can crack the joints in the drywall.
I then cut pieces to fit in the spaces between framing members:
And then covered the framing again on the inside. This gave me three layers for a total of 3″ of polyurethane foam which is roughly R12. I used spray foam to fill the gaps in the corners.
I covered this with 1/2″ drywall. Seen here is how I held the framing back 1/2″ to allow for the drywall:
I used plywood to make a ‘jamb’ that is against the skylight. I don’t like to put the drywall up that far, even if it has j-trim. The plywood / drywall junction will be mudded and taped, just like the rest of the drywall in the well.
Finish patching the drywall and put on metal corner beads then the first coats of mud are applied, it’s starting to look like the real deal:
In order to make the installation match the ceiling, I had to make the ceiling smooth.
As seen on the previous photos, the ceiling originally had a spray-on texture and I know from experience that it is impossible to patch this and make it look good. I used a paint scraper and trowel to knock the high spots off, then gave it 2 coats of drywall compound, sanding after each coat. Thankfully it was not a large area!
The ceiling was remarkably smooth after this and it is impossible to tell that the skylight wasn’t always there.